Here is a thread on r/Teachers where teachers discuss how many hours they work [1]. From a quick skimming it seems to vary with new teachers working really hard, older ones having pretty easy hours, and some teachers doing things like extracurriculars which are not difficult but do take time.

[1] https://www.reddit.com/r/Teachers/comments/6f1m76/how_many_h...

I know this is a biased sample.